Method and apparatus for controlling well fluids



| J. OBRIEN 3,294,169

METHOD AND APPARATUS FOR CONTROLLING WELL FLUIDS Dec. 27, 1966 2Sheets-Sheet 1 Filed Dec. 17, 1962 INVENTOR. LEO J. O'BRIEN BY 4mm4ATTORNEY.

FIG.2

Dec. 27, 1966 1.. J. O'BRIEN 3,294,169

METHOD AND APPARATUS FOR CONTROLLING WELL FLUIDS Filed Dec. 17, 1962 2Sheets-Sheet 2 F I G. 8 ATTORNLE United States Patent 3,294,169 METHODAND APPARATUS FOR CONTROLLING WELL FLUIDS Leo J. OBrien, Crystal Lake,1., assignor, by mesne assignments, to Union Oil Company of California,Los Angeles, Calif., a corporation of California Filed Dec. 17, 1962,Ser. No. 244,959 12 Claims. (Cl. 16646) This invention relates to amethod and apparatus for controlling the flow of fluid in wells and theadjacent formation. One aspect of the invention relates to the controlof flow of fluid between a well and an adjacent formation. Anotheraspect of the invention relates to the control of flow of fluid betweenvertically adjacent zones of a well bore.

The prior air recognizes the need for controlling the flow of fluidbetween a well and a surrounding permeable formation in both drillingand producing operations. Prior art techniques employed have includedthe plugging of formations, the casing of well bores, and the forming ofmud filtrate sheaths. The prior art also recognizes the necessity forcontrolling the flow of fluid between adjacent zones of a well bore. Forexample, in fluid injection, acidizing, and fracturing operations, it isusually desired to pressurize only a selected section of the well.Numerous kinds of packers designed to meet this need have proved to bereasonably satisfactory for use in cased wells. In uncased wells,satisfactory packing is difficult to achieve.

It is an object of this invention to provide a method and apparatus forthe control of fluid flow between a well bore and the encompassingformation. It is another object of this invention to provide anapparatus and method for controlling flow of fluids between adjacentzones of a well. Another object of this invention is to provide packingand casing means which are easily installed and removed for use in wellbores. Other objects of the invention will become apparent from thefollowing description, which is made with reference to the drawings, ofwhich:

FIGURE 1 is a sectional view of a well bore in which is disposed a drillstring and means for controlling flow of fluids from the well bore tothe formation in accordance with this invention.

FIGURE 2 is a view of FIGURE 1 taken in the direction 2-2,

FIGURE 3 is a sectional view of an apparatus usefu in the method of thisinvention in drilling and packing operations,

FIGURE 4 is a view of valve means forming a part of the apparatus ofFIGURE 3,

FIGURE 5 is a sectional view of a packer useful in accordance with thisinvention,

FIGURE 6 is a sectional view of an alternate packer structure,

FIGURE 7 is a sectional view of a double packer particularly adapted foruse in formation fracturing operations, and

FIGURE 8 is a sectional view of a well bore provided with a temporarycasing in accordance with this invention.

The method of this invention utilizes electric field-responsive fluids,commonly called electrofluids, which display a dramatic increase inapparent viscosity in the presence of an electric field. The fluidsthemselves form no part of this invention, but are well known in the artand described in patents and in the literature e.g., Winslow 2,417,850and 3,047,507. Some such fluids are produced by incorporating finelydivided particulate solids, such as finely powdered silica, in adielectric fluid, which is usually a refined'hydrocarbon, such as whiteoil, or a lower viscosity lubricating oil fraction. Various additivesmay be incorporated in such fluids to serve different purposes.

For example, it is usual to incorporate a fluidizing agent which permitsthe use of greater quantities of particulate solids without raising theresidual viscosity of the product to an undesirably high level. Where itis desired to employ a DC rather than an AC. field to activate thefluid, small amounts of basic nitrogen-containing compounds are usuallyadded. In the practice of the instant invention, where large quantitiesof field-responsive fluids are required, and a rather high residualviscosity is desirable, it is preferred to keep the use of additives toa minimum. For this purpose, it is also preferred to use alternatingpotential to control the apparent viscosity of the electrofluid in thewell bore. Where little or no fluidizer or basic nitrogen compounds havebeen added, the tendency of the fluid to emulsify upon contact withformation Water is reduced.

Referring to FIGURE 1, formation 10 is penetrated by well bore 12, inwhich is disposed drill string 14. The well bore has penetrated aformation zone 16 of high permeability, which result in considerablefluid loss to the formation and difliculty in maintaining drilling fluidcirculation. To meet this problem, drill string 14 has been equippedwith assembly 20 which comprises a section of drill pipe 22, a tubular,electrically conducting electrode 24 which encompasses pipe section 22,bearings 26, 28' and bearing retainer assemblies 26 and 28 which aredisposed at opposite ends of electrode 24, and electrically insulatingspacer 30 and 32 which serve to electrically insulate pipe section 22from the remainder of the drill string. The electrode is supported frominsulators 30 and 32 by means of frangible spokes such as spokes 34 and36. A plurality of longitudinal spacers is provided externally ofelectrode 24. These spacers, which are shown best in FIGURE 2 anddesignated by numeral 38, are longitudinal stringers which arefabricated of an electrically insulating material. They function toretain the electrode 24 in electrically insulated relationship withrespect to the well bore.

An electrical circuit, including a potential source comprising generator43, variable resistance 45, switches 44 and 49, and ground stake 51, incooperation with electrical conductors 53 and 55, provides means forapplying an electric potential between electrode 24 and pipe section 22,or between electrode 24 and the wall of well bore 12. In the lattercase, the electrical connection is maintained between the stake and thewell bore by the natural conductivity of the earth. Conductors 53 and 55may be a part of the drill string, as described in US. Patent No.2,178,931.

In operation, the assembly is lowered to a position adjacent theformation zone of high permeability, as shown in FIGURE 1. An electricfield-responsive fluid is then introduced through the annulus betweenthe drill string and the wall of the well bore. Since the fluid tends topreferentially enter the larger space between electrode 24 and insulatedpipe section 22, a high electric potential is applied between electrode24 and pipe section 22 by closing switch 44 and operating switch 49 toconnect potential source 43'to conductor 55. It will be understood thatconductor 53 connects to electrode 24, while conductor 55 connects topipe section 22. Fluid in the space between the electrode and pipesection is thereby rendered very viscous, or semi-solid, which preventsfurther flow of fluid upward between the electrode-and drill stem, anddirects the fluid upward between the electrode and well-bore. Thus, aneconomy of fluid is achieved.

After the annular space between the electrode and well-bore has beenfilled with the electric field-responsive fluid, a high potential in therange of about 50,000 to 3 250,000 volts per inch of radial distancebetween the electrode and well bore is applied by connecting switch 49to ground stake 51. The fluid in the annular space between the electrodeand well bore is thereby rendered solid, or at least semi-solid, and theelectrode secured firmly in place. Since the fluid between the electrodeand pipe section 22 is no longer energized, the drill string may berotated to shatter frangible spokes 34 and 36 and to break conductor 55lose from pipe section 22. Drilling fluid may be pumped down the drillstring and drilling may then proceed in the usual manner. The electrode24, acting in conjunction with the annular column of electricfield-responsive fluid, will retain an effective seal at the wellinterface with formation zone 16 so long as a high electric potential ismaintained. Circulation of drilling fluid and cuttings upward throughthe space between the electrode and drill string can be maintained inthe usual manner. Bearings 26' and 28' and bearing retainer assemblies26 and 28 are provided to maintain the electrically insulatedrelationship between the electrode and drill string and to preventbinding of the drill string and electrode in the event the drill stringdoes not remain central in the well bore. The interior member of thebearing assembly is, of course, fabricated of an electrically insulatingmaterial, such as polyfluoroethylene. When it is desired to remove thedrill string from the well bore, the electric potential is disconnectedand the electrode 24 is pulled upward with the drill bit.

An alternate apparatus for use in conjunction with a drilling string ora tubing string is depicted in FIGURES 3 and 4., Threaded tubing section40 is adapted for connection in a drill string. Electrical conductors 41and 42 extend downward through the well boreexternally of the drillstring and make connection to the apparatus as will later appear. Pipesection 40 is surrounded by spoolshaped member 46, which is supporteddirectly from pipe 40 and is fabricated of an electrically insulatingmaterial, such as plastic. Outside of and annular to member 46 istubular electrode 48, which is fabricated of steel. Electrode 48 may beof any desired length, and is of a diameter such that it willconveniently fit within the well bore. Electrode 48 is retained inposition and rotatably supported from pipe section 40 by means offlanges 50 and 56 of spool-shaped member 46, in cooperation with metalraceways 58 and 59 and the complementary raceways 60 and 61 which areformed in electrode 48. Ball bearings 62 and 64 complete the supportingassembly. Conduit 42 makes electrical connection to metal raceway 58,and then through ball bearing 62 to electrode 48.

Perforated ring 52 cooperates with flange 50 to form a valve forcontrolling flow of fluid through annulus 65 axially of the pipe section40. Ring 52 is supported by element 46 and is readily rotatable viabearing 66 and raceway 67. Referring to FIGURE 4, flange 50 and ring 52are seen to be perforated by a plurality of holes indicated generally bythe numerals 70 and 74, '70 indicating perforations in flange 50 and 74indicating perforations in disc 52. Flange 56 is similarly perforated.It is evident that when the holes 70 and 74 are rotatably displaced fromeach other, flow of fluid axially of the packer is prevented. On theother hand, when holes 70 and 74 are brought into registry, it isevident that fluids may flow through openings in flange 56, throughannular space 65,

' and thence through the valve formed by ring 52 and flange 50. Whilethe valve formed by ring 52 and flange 50 may be operated by mechanicalor hydraulic means for rotating ring 52, electrical actuation ispreferred. For example, a solenoid, not shown in the drawing, may besupported from member 46 and used to drive ring 52. The solenoid may beenergized through conductor 41, which may carry two wires and thusprovide power to the solenoid, or conductor 41 may carry only a singlewire and 'the drill string used as a return lead. It will be evidentthat numerous other valve means may be employed. In practice, it isdesirable that the openings 70 and 74 be of the greatest possiblecross-sectional area so that the valve means, when opened, will provideminimum resistance to flow.

Referring to FIGURE 5, a packer useful in fracturing and oxidizingoperations is shown. Formation 78 is penetrated by well bore 80, inwhich is inserted tubing string 82. The lower portion of the tubingstring 82 supports electrically insulating blocks 86 and 88 which, inturn, support tubular electrode 90. Electrical conductor 91 is providedto energize electrode 510. In operation, the tubing string is loweredinto a well bore adjacent the bottom thereof, or adjacent to a packerwhich seals off a lower portion of the well bore, and electric potentialresponsive fluid is pumped downward through the tubing string and upwardin the annulus surrounding electrode 90. Electric potential is thenapplied between ground and electrode 00 by means of conductor 91. Apotential source similar to that shown in FIGURE 1 may be employed. Theannularly shaped column of electrofluid 94 is energized and renderedsemi-solid by the applied potential. Electrofluid in the Well bore belowelectrode may be removed by baling. Fracturing fluid is then introducedinto the space below electrode 90 through the tubing string, andpressure applied to fracture'the formation in the conventional manner.The potential source may then be disconnected and the apparatuswithdrawn from the well bore. If desired, insulating rings 88 may bereplaced with valve means as shown in FIGURES 3 and 4, whereby theelectrofluid below electrode 90 may be dis placed upward through annularspace 96 by the injection of fracturing liquid. In this case, theinterior surface of tubular electrode 90 should be protected by a layerof electrically insulating material to prevent solidification ofelectrofluid within the annulus, in the event the tubing string isgrounded.

Referring to FIGURE 6, a simple packer is shown to comprise tubingstring 100, spool 102 which is fabricated of an insulating material,cylindrical screen 104, conductor 106, and frangible disc .108. To setthis packer, the assembly is lowered into the well-bore and electrofluidis introduced under pressure down the tubing string and through openings107 and 109 in the tubing string and spool, respectively. Theelectrofluid flows outward through screen 104, whereupon electricpotential is applied by means of conductor 106 to freeze the packer inplace by solidifying the electrofluid. The tubing string can then berotated to bring holes 107 out of alignment with holes 109, and higherpressure applied to break frangible disc 108.

Referring to FIGURE.7, a double packer, useful in fracturing andacidizing formations at locations above the bottom of the well bore, isshown. It will be assumed that a decision is reached that well bore 110,which penetrates formation 112, should be fractured at position 114. Atubing string supporting the apparatus shown in FIG- URE 7 is loweredinto well bore 110. Inner tubing section 116 is provided with apertures117 and rupture discs 118 in the pipe at about the center of its length.An outer tube 120 which is fabricated of an electrically insulatingmaterial, preferably a suitable plastic, has perforations 122 at aboutthe center of its length, and is spaced annularly to tube section 116with perforations 1'22 adjacent to rupture discs 118. Outer tube 120 isspaced and insulated from inner tube section 116 by electricallyinsulating spacers 124, which are fabricated of a suitable plastic.Tubular electrodes 128 and 129 are supported externally of outer tube120 above and below perforations 122. Electric potential can be appliedto electrodes 128 and 129 by means of conductor 130, wherebyelectrofluid surrounding electrodes 128 and 129 may be energized. Thelower extremity of tubing section 116 is closed by valve 131.

Means for centering the apparatus within the well bore may be provided,as shown in FIGURES 1 and 2. Alternatively, tubing string centeringdevices, well known in the art, may be provided on the tubing stringabove and below the apparatus of this invention, whereby propercentering is achieved. In operation, with valve 131 closed, electrofluidis pumped down the tubing string and sufficient pressure is applied torupture the rupture discs 11 8. The electrofluid passes out throughperforations 117 and 122 and into the annular space of the bore. At thistime the electrodes are preferably energized by a small potential, say50,000 volts per inch of radial space be tween the electrode and thesurrounding well bore, whereupon the electrofluid in the space betweenthe electrodes and well bore will become very viscous, but not immobile.Application of pressure is continued until the annular spaces 134 and 136 are filled with viscous electrofluid. Pressure is then relieved andthe applied potential is increased to a value in the range of 50,000 to250,000 volts per inch of radial annular distance between the electrodesand well bore wall. The valve 131 may then be opened to purgeelectrofluid from the tubing string by force of gravity, and fracturingfluid is then introduced through the tubing string and into the wellbore zone 138 between electrodes 128 and 129. At this time valve 131 is,of course, closed. Fracturing of the formation is then carried out inthe usual manner. It will be evident that since the electrofluid is notdetrimental to the fracturing process, and since the fluid in any eventis present in small amounts, the process may be carried out without everopening valve 131, and indeed valve 131' can be replaced by means forclosing the tubing section 116 below ports 117.

Referring to FIGURE 8, a well bore is provided with a temporary wellcasing in accordance with the teachings of this invention. Threadedcasing sections 212, which form a portion of a well casing, are loweredirito well bore 210. Each section of the casing is novel in that it hasan inner pipe 218 composed of an electrically nonconducting material,preferably a suitable plastic, and an outer metal pipe section 220 thatis electrically conducting. Cement shoe 222 is threaded into the bottomof the casing. Cement shoe 222 features valve 224 that permits flow ofcementing material downward through the shoe but checks upward flow. Thecasing string is lowered into the well bore. Next, cement plug 226,featuring rupture disc 228, is lowered to seat on cement shoe 222. Asuitable amount of an electric field-responsive fluid is injected tojust fill the annulus between the metal pipe sections which comprise thecasing, and the well bore. Snugly fitting cement plug 230 is thenlowered into the casing, and rests upon the measured volume of electricfield-responsive fluid. Suitable pressure is exerted upon the plug 230to rupture disc 228 and force electrofluid out through one-way valve 224and into the annulus of the well surrounding the casing. When theannulus is filled, a high electric potential in the range of 50,000 to250,000 volts per radial inch of distance between the casing and wellbore is imposed upon the easing and ground, whereby the electrofluid isenergized. The high potential freezes the electrofluid into a solid orsemi-solid condition, effecting a temporary cementing. At a later date,if desired, the electric potential may be removed, which will againrender the electric field-responsive fluid flowable, and make possiblethe salvage of the temporary casing, as well as most of theelectrofluid.

In the practice of this invention, it is contemplated that any of thewide variety of art-recognized electric fieldresponsive fluids may beemployed. A suitable non-limiting example of such a fluid is thatdisclosed in US. Patent 3,047,507 to Winslow as Example No. 15. Also,while the application of the electric field has been illustrated byapplying a potential between an electrode and ground, using the naturalconductivity of the earth, it will be evident that other means forapplying an electric field to the electric field-responsive fluid may beemployed.

For example, a plurality of electrodes may be disposed downhole incontact with the fluid, and electric potential applied to theseelectrodes.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. The method of controlling the flow of fluid between a well bore and asurrounding formation comprising disposing an elongated tubularelectrode within said well bore in substantially coaxiaily alignedrelation therewith, to form an annular space between said electrode andthe walls of the well bore, disposing within said annular space a fluidthat exhibits a change in apparent viscosity upon the application of anelectric fluid, providing means by which an electric field may beapplied across said fluid, and applying an electric field radially ofsaid annular space.

2. The method in accordance with claim 1 in which said field is appliedby connecting a potential source between said electrode and ground.

3. The method in accordance with claim 2 in which the magnitude of theapplied potential is in the range of 50,000 to 250,000 volts per inch ofradial distance between said electrode and the wall of said well-bore.

4. The method of isolating a well bore zone from an axially adjacentwell bore zone comprising disposing a cylindrical member within saidwell bore between said zones, in spaced relationship with said well boreto form an annular space therebe tween, said cylindrical member beingsubstantially impermeable to fluid flow in axial direction, disposing inthe annular space a fluid that exhibits -a change in apparent viscosityupon the application of an electric field, providing means by which anelectric field may be applied across said fluid, and applying anelectric field transversely of said annular space.

5. The method in accordance with claim 4 in which the peripheral surfaceof said cylindrical member is conductive and said field is applied byconnecting an electric potential between said surface and ground.

6. The method in accordance with claim 5 in which the magnitude of theapplied potential is in the range of 50,000 to 250,000 volts per inch ofradial distance between said peripheral surface and the wall of saidwell-bore.

7. The method of isolating a well bore zone from an axially adjacentwell bore zone comprising supporting a cylindrical packing member inaxially aligned, encompassing, fluid-tight relationship with respect toa tubing string, disposing said tubing string within said well bore tosupport the packing member between said well-bore zones and in spacedrelationship with respect to the walls of said well-bore, disposing inthe space between said member and the walls of said well bore a fluidthat exhibits a change in apparent viscosity upon the application of anelectric field, providing means by which an electric field may beapplied across said fluid, and applying an electric field radially ofsaid space.

8. The method in accordance with claim 7 in which the peripheral surfaceof said cylindrical member is conductive and said electric field isapplied by connecting an electric potential between said surface andground.

9. The method in accordance with claim 8 in which the magnitude of theapplied potential is in the range of 50,000 to 250,000 volts per inch ofradial distance between said electrode and the wall of said well bore.

10. A cased well comprising a well bore, a steel casing of diametersmaller than said well bore disposed therein concentrically therewith toprovide an annular space between the walls of said well-bore and saidcasing, a column of a fluid that exhibits a change in apparent viscosityupon application of an electric field disposed within said annularspace, and means for applying an electric potential between said casingand ground.

11. In a drilling apparatus for disposition in a well bore including adrilling string, a section of drill pipe connected in said string, meanselectrically insulating said section of pipe from the remainder of thedrill string, a tubular electrode encompassing said section of pipe, tothereby form an annular space therebetween, said section of pipe andelectrode being adapted to support in said annular space a fluid thatexhibits a change in apparent viscosity upon the application of anelectric field, means secured to said pipe for supporting said electrodein electrically insulating relationship and substantially concentricallyWith respect to said pipe, and means connected to said section of pipeand electrode for applying an electric potential between said electrodeand said section of pipe.

12. An apparatus in aco'rdance with claim 11 including bearing meansdisposed internally of said electrode adja- References Cited by theExaminer UNITED STATES PATENTS 2,118,669 5/1938 Grebe 204- 180 2,217,85710/1940 Byck 204-180 2,283,206 5/1942 Hayward 204 -180 2,625,374 1/1953Neuman 20'4-180 2,799,641 7/1957 Bell 204-180 FOREIGN PATENTS 505,7095/1939 Great Britain. 650,753 3/ 1951 Great Britain.

OTHER REFERENCES I Rogers, Composition and Properties of Oil WellDrillcent each end thereof, said bearing means being secured 15 ingFluids, first edition, 1 4 Gulf Publishing Co Hons.

to said section of pipe and having a ring structure mounted thereon,said bearing means being rotatable with respect to said ring structure,said bearing means and said ring structure having flu-id passagewayswhich upon registry permits communication of said annular space to saidwell bore.

ton, Texas, page 388. CHARLES E. OCONNELL, Primary Examiner.

2O JACOB L. NACKENOFF, Examiner.

T. A. ZALENSKI, D. H. BROWN, AssistantExaminers.

4. THE METHOD OF ISOLATING A WELL BORE ZONE FROM AN AXIALLY ADJACENTWELL BORE ZONE COMPRISING DISPOSING A CYLINDRICAL MEMBER WITHIN SAIDWELL BORE BETWEEN SAID ZONES, IN SPACED RELATIONSHIP WITH SAID WELL BORETO FORM AN ANNULAR SPACE THEREBETWEEN, SAID CYLINDRICAL MEMBER BEINGSUBSTANTIALLY IMPERMEABLE TO FLUID FLOW IN AXIAL DIRECTION, DISPOSING INTHE ANNULAR SPACE A FLUID THAT EXHIBITS A CHANGE IN APPARENT VISCOSITYUPON THE APPLICATION OF AN ELECTRIC FIELD, PROVIDING MEANS BY WHICH ANELECTRIC FIELD MAY BE APPLIED ACROSS SAID FLUID, AND APPLYING ANELECTRIC FIELD TRANSVERSELY OF SAID ANNULAR SPACE.